Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
  • C04B28/06—Aluminous cements
  • C04B28/065—Calcium aluminosulfate cements, e.g. cements hydrating into ettringite
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B7/00—Hydraulic cements
  • C04B7/02—Portland cement
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/32—Expansion-inhibited materials
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/34—Non-shrinking or non-cracking materials

Definitions

• This invention relates to improvements in the composition of hydraulic cement. More particularly, it relates to improvements in cement which consists of blends o Portland cement, calcium aluminate cement and a sulfate compound, preferably of a calcium or aluminum sulfate or gypsum.
• hydroaulic cement as used herein is intended to mean portland cements, expansive cements, air entraining portland cements, pozzolanic cements, slag cement masonry cement, white portland cement, colored cement, antibacterial cement, waterproof cement, refractory cement, self-stressing cement, aluminous cement, and similar materials.
• gypsum as used herein is intended to include gypsum such as is normally understood in the art. This would include calcium sulfate (CaSO ) and its various forms such .as calcium sulfate anhydrate, calcium sulfate hemihydrate, and calcium sulfate dihydrate, as well as calcined gypsum, pressure calcined gypsum, and plaster of Paris.
• CaSO calcium sulfate
• aluminous cement as used herein is intended to include those cementitious materials normally understood in the art to contain as the main cementitious constituent, mono calcium aluminate (CaO x Al 0 ) . This would include high alumina cement (HAC) , calcium aluminate cement, and many other commercially available alumina cements.
• HAC high alumina cement
• the term "Portland cement” as used herein is intended to include those cements normally understood in th art to be “Portland cement,” such as those described in AST Standard C-150.
• the Portland cement component of these cementitious mixtures acts to reduce drying shrinkage and increase wet expansion.
• Other cements which act as drying shrinkage inhibitors although not specifically referred to as Portland cement, are also suitable for use herein so tha the term “Portland Cement” should be understood as encompassing those other cements.
• drying shrinkage inhibitors include expansion promoters such as expansive cements which are compatible with the other constituents of the system.
• a cementitious composition comprising a mixture of an aluminou cement, a gypsum, a drying shrinkage inhibitor, and a wet expansion inhibitor.
• the compositions of that invention preferably use Portland cement as a drying shrinkage inhibitor and a lithium salt as the wet expansion inhibitor.
• various accelerators, retarders and other admixtures when added to aluminous cement and gypsum compositions, can significantly affect the hardened volume change (wet or dry) , thus limiting their usefulness.
• U.S. Patent No. 4,045,237 discloses a cementitious composition which, when mixed with water, is capable of setting into a hard mass in a short period of time without substantial shrinkage during setting and early hardening an possessing a high degree of impermeability to fluids.
• the composition comprises a particulate admixture of calcined gypsum, high alumina cement and portland cement, or it may comprise a mixture of particles of high alumina cement and pressure calcined gypsum, without the use of Portland cemen
• Portland cement consists mainly of tri-calcium silicate and dicalcium silicate.
• two types of raw materials are usually required - one high calcium content, such as limestone or chalk, and the other rich in silica, such as clay or shale.
• These raw materials ordinarially contain an appreciable concentration of iron- bearing compounds. The presence of these compounds during the heating process leads to the formation of a clinker containing several percent of iron oxide.
• This Portland cement clinker will therefore, vary considerably due to variations in the composition and particle size of the raw materials as well a inconsistencies in the burning conditions, which leads to variations in clinker porosity as well as differences in crystalline sizes and forms found in the aggregates of crystallites.
• the Portland cement component of the cementitious compositions disclosed in U.S. Patent Nos. 4,357,166 and 4,045,237 contains an appreciable quantity of iron oxide as described above.
• U.S. Patent No. 4,045,237 for example, it is critical to employ between 0.1-10% of Portland cement in the mixture.
• the addition of greater tha 10% of Portland cement leads to difficulties with the cement hydration reactions due to the resulting proportion of ferri oxide in the Portland cement-calcined gypsum-high alumina cement mixture.
• U.S. Patent No. 4,157,263 which is a division of the application leading to the issuance of the '237 patent discloses a method for using the compositions claimed in the ' 221 patent for use in repairing and waterproofing concrete structures and for filling voids and holes to form stable underpinnings or foundations for machinery or heavy equipment.
• the Portland cement utilized in the performance of this method contains, as noted above, appreciable quantities of ferric oxide, which restricts the amount of Portland cement which may be added to the mixture, thus reducing the strength of the composition.
• the maximum iron oxide content may vary, but as a general principle it should be a maximum of about 2 weight percent. Preferably, the iron oxide content should be as lo as possible, but as a practical matter, amounts lower than 0.1 weight percent are difficult to achieve.
• This invention relates to improvements in the composition of hydraulic cement. More particularly it relates to improvements in cement which consists of blends o Portland cement, calcium aluminate cement and a calcium or aluminum sulfate compound.
• composition disclosed by the applicants comprises from about 0.1 to about 80 parts by weight of a Portland cement manufactured from raw materials containing' low levels of iron compounds so as to have a low iron oxide content; from about 0.1 to about 40 parts by weight of a sulfate compound, preferably gypsum, and from about 2 to about 90 parts by weight of an aluminous cement.
• the most advantageous composition includes about 2 to 20 parts by weight of the low iron Portland cement, 55 to 95 parts by weight of the aluminous cement and 2 to 10 parts by weight o gypsum.
• sulfate compound While any sulfate compound can be used in this invention, organic or inorganic sulfate salts are preferred.
• Calcium sulfate provides the best results and is the most advantageous whether used as a pure chemical, formed in situ or added in its common form, gypsum.
• Aluminum ammonium sulfate (A1NH.(S0.) ) and aluminum potassium sulfate (A1K (SO.),,) also provide good results.
• Other alkali metal sulfates have not been found to be useful, and satisfactory performance is found only with the calcium and/or aluminum 5 sulfates. Due to its availability, gypsum in any of its various forms, is most advantageous sulfate compound.
• cementitious composition In one embodiment of the cementitious composition,
• the maximum iron oxide content of the Portland cement is 2 weight percent, measured as ferric oxide according to ASTM test method C-114.
• the gypsum selected for use in applicants' * composition is calcium sulfate hemihydrate.
• composition may further comprise a number of additional ingredients and additives, which may include up to about 90% by weight of an aggregate based upon a total weight of Portland cement, sulfate compound and aluminous cement in the composition.
• Additional ingredients may include a compound capable of generating a volume of gas upon contact with water, a surface active agent, a water reducing agent and a set time controlling agent.
• 30 therefore comprises from about 0.1 to about 80, and preferably 2 to 20, parts by weight of a Portland cement having a maximum iron oxide content of 2 weight percent; from
• Applicants have also discovered a novel method for producing their volume-stable cementitious composition which comprises blending, for a predetermined duration, a mixture comprising from about 0.1 to about 80 parts by weight of a Portland cement manufactured from raw materials containing low levels of iron compounds so as to contain less than abou 2% of iron oxide; from about 0.1 to about 40 parts by weight of a calcium or aluminum sulfate compound and from about 2 t about 90 parts of weight of aluminous cement, and thereafter hydrating this mixture with water.
• the method developed by the applicants may include several additional steps, which include adding to the mixtur an amount of from about 1 to about 90 parts by weight of an aggregate based upon the total weight of Portland cement, sulfate compound and aluminous cement before hydrating the mixture with water.
• one may also add to the mixture at least one of an accelerator, a retarder, a pigment, a water reducer or a gas generating agent.
• the improvement in the cementitious composition disclosed by applicant comprises controlling the maximum iro content of the Portland cement to about 2 weight percent in order to obtain improved volume stability, higher strength and better bonding strength to other cementitious co postions.
• the improvement further comprises decreasing the setting time for the composition by reducing the iron oxide content of the cement to as low a value as possible.
• the iron oxide content should range between 0.1 and 2 weight percent in applicants' composition.
• a composition comprising calcium aluminate cement, calcium sulfate hemihydrate and portland cement wherein the ortland cement was manufactured from compounds containing a "normal" amount of ferric oxide, about 23 weight percent, is utilized.
• Dry shrinkage 0.0196% after 14 days storage at 50% humidity
• Dry shrinkage 0.0003% after 14 days storage at 50% humidity
• Wet expansion 0.0004% after immersion in water
• a 50% increase in bonding strength over the composition as described in Example 1 was also noted as well as a drastic decrease in the water absorption and permeability of the hydrated product.
• Examples 3 and 4 further show the improvement that low iron oxide Portland cements provide.
• Example 3 the following ingredients were dry blended for one minute:
• the Portland cement contained about 23 weight percent ferric oxide. After dry mixing, 12.5% water was added to hydrate the mix and the following characteristics were determined:
• Example 3 The components used in Example 3 were once again utilized i the same proportions. In this example, however, the Portla cement was manufactured from raw materials containing low levels of iron compounds as in Examples 2 (i.e., a ferric oxide content of 0.4 weight percent).
• the Melment F-10 compound used in the examples is a well-known water reduci agent which is available from American Admixtures, Chicago, Illinois. Other water reducing agents can also be used in this invention.
• the normal additives that are added to concrete can, of course, be use These include, but are not limited to, accelerators, retarders, pigments, air entraining agents, water reducers, pumping aids, fly ash, gas generating and releasing agents and, of course, the full range of aggregates. 1?

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Inorganic Chemistry (AREA)
• Curing Cements, Concrete, And Artificial Stone (AREA)

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• 1987
  • 1987-03-24 BR BR8706658A patent/BR8706658A/pt unknown
  • 1987-03-24 CA CA000532828A patent/CA1279332C/fr not_active Expired - Lifetime
  • 1987-03-24 AU AU72099/87A patent/AU7209987A/en not_active Abandoned
  • 1987-03-24 JP JP62502179A patent/JPH0776121B2/ja not_active Expired - Fee Related
  • 1987-03-24 WO PCT/US1987/000638 patent/WO1987005893A1/fr not_active Application Discontinuation
  • 1987-03-24 EP EP19870902939 patent/EP0270565A4/fr not_active Withdrawn

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